Heating plate for vacuum filter press

ABSTRACT

A filter press ( 11 ) defined by a closable stack of filter plates defined by a first plurality of membrane filter plates ( 21 ) alternately disposed with a second plurality of heating-type filter plates ( 22 ). The membrane plates ( 21 ) have chamber-defining recesses on opposite sides thereof, with each recess ( 36 ) having a flexible membrane ( 39 ) associated therewith which can be pressurized from the rearward side so as to effect squeezing of the cake in the filtration chamber. Each heating plate ( 22 ) also has chamber-defining recesses ( 74 ) on opposite sides thereof, and the main center bottom wall ( 76 ) of each recess ( 74 ) has a metal heat transfer surface ( 77 ) associated therewith, the rear side of which is in intimate contact with a chamber or passage ( 79 ) which receives therein a high-temperature heat transfer fluid.

FIELD OF THE INVENTION

This invention relates to a filter press for dewatering slurry and, morespecifically, to an improved filter press for permitting heating anddrying of filter cake formed in filtration chambers of a filter press topermit more efficient separation of liquid from slurry, and the methodfor effecting such separation.

BACKGROUND OF THE INVENTION

Filter presses are well known and extensively utilized for separatingsolids from slurries. Such filter presses employ a plurality of filterplates which are held in contacting relationship between fixed andmovable head members while the slurry is pumped into and through thepress for collecting the solids in the form of cake between adjacentfilter plates. When the press is full, the movable head is backed awayfrom the plates into an open position and the plates are moved into anopen position to permit discharge of the cake which is collected betweenadjacent pairs of plates. To permit movement of the plates into an openposition, plate shifting mechanisms are typically provided adjacentopposite sides of the press for permitting automatic or manual controlover the plate movement and cake discharge.

Various types of filter plates are utilized in filter presses, dependingprimarily upon the material to be filtered and the process requirements.For example, one type of plate is a cloth-type chamber plate whichincludes recessed surfaces on opposite sides of the plate, each of whichserves to form a filter chamber with an adjacent plate when the platesare clamped together. A cloth filter covers each of these recessedsurfaces, and is either mounted on the plate by a gasket or is drapedbetween two adjacent plates. Thus, slurry is pumped into the filterchambers formed between the filter cloths of two adjacent plates, andthe liquid from the slurry passes through the filter cloth and isdischarged through filtrate ports in the plates. The solids are trappedin the filter chamber and form a cake.

Another type of filter plate which is utilized when process requirementscall for production of a dryer filter cake is a membrane ordiaphragm-type squeeze plate. The construction of this type of plate issimilar to the cloth-type chamber plate, but the drainage surfaces onthe opposite faces of the plate are flexible diaphragms or membraneswhich define pressurizing chambers therebehind. A filter cloth coversthe outer face of the diaphragm on each side of the plate and typicallyextends beyond the plate, i.e., the filter cloths are typically drapedbetween the adjacent plates. In this case, slurry is pumped into thefilter chambers formed between two neighboring plates and the liquidportion of the slurry passes through the filter cloths and is dischargedthrough filtrate ports in the plates. After the filling cycle iscomplete and the filter chambers formed between adjacent plates arefilled with solids, and before the press is opened, pressurized air orwater is supplied to the chamber located behind each diaphragm, causingthe diaphragms to flex outward and exert mechanical pressure on thefilter cake. This also effects limited heating of the filter cake which,in conjunction with a vacuum applied to the discharge side of the filtercloths, causes additional moisture to be removed from the filter cake.An example of this type of arrangement and process is disclosed in U.S.Pat. No. 5,558,773. A similar press and process is also sold by theassignee hereof under the designation “J-VAP”.

While filter presses employing membrane-type filter plates have providedimprovement with respect to removal of liquid from the filter cake,nevertheless such membrane-type filter plates are of limited capabilitywith respect to their ability to provide effective heating of the filtercake to assist in moisture removal by vaporization. It accordingly hasbeen proposed to modify the filter press to include heating plates inconjunction with membrane-type filter plates. In such proposal, asillustrated by U.S. Pat. No. 6,387,282, a plurality of rigid metalheating plates are alternately interposed between the plurality ofconventional membrane-type filter plates. Each heating plate is henceclamped between a pair of membrane-type plates when the filter press isclosed, whereby each filter chamber is defined between the opposed facesof the adjacent membrane-type filter plate and the adjacent heatingplate, and the size of the filtration chamber and hence the capacitythereof is defined principally by the recess formed in the membrane-typefilter plate inasmuch as the opposed surface on the heating plate istypically flat. Since the heating plate is constructed of metal and hasinterior chambers and passages for accommodating a high-temperatureheating fluid therein, such heating plate is effective in permittingtransfer of significant quantities of heat energy through the metal faceof the heating plate into the adjacent filter cake. Such arrangementhence does permit increased heating and accordingly more effectivevaporization of the liquid in the filter cake, whereby more effectiveremoval of liquid from the filter cake can be achieved.

With a filter press employing alternating metal heating plates of thetype described above, however, the overall construction of the filterpress, in order to maintain the same press capacity, increasessignificantly with respect to the structure and size thereof since thesame number of membrane-type filter plates must be maintained, and atthe same time a substantially similar number of heating plates areincorporated into the press, thereby significantly increasing theoverall size (i.e., length) and also the space requirements and cost ofthe press.

In addition, in a press having alternating membrane-type and metalheating plates as mentioned above, the heating plates are constructedsubstantially entirely of metal and function solely to provide heat tothe filter cake, but are not designed to cooperate with or promote otherrequired or desired operational features of the press. For example, themetal heating plates are not provided with ports or openings whichcommunicate with the adjacent filtration chamber, whereby all drainageof liquid from the filtration chamber must occur through ports locatedsolely adjacent one side thereof, namely through ports provided in themembrane-type filter plate. This restricts the ability of the press toeffect efficient drainage of liquid from the filtration chamber. Thisalso restricts the effective use of air blow into and through the filtercake to further assist in vapor removal since the only ports availablefor air blow are provided on one side of the filtration chamber, namelyin the membrane filter plate, and as such the air blow can effectmovement of air only transversely across the filter cake and notlongitudinally through the thickness thereof, whereby the effectivenessof the air blow is believed significantly impaired.

Other examples of plate-type filter presses employing heating plates toprovide more effective heating of filter cake within the press areillustrated by U.S. Pat. No. 4,999,118, U.S. Pat. No. 1,049,715, and PCTPublication WO 95/27550.

It is an object of the present invention to provide an improved filterpress which overcomes or minimizes the disadvantages associated withprior press constructions, as briefly discussed above.

More specifically, it is an object of this invention to provide animproved filter press employing both membrane filter plates and heatingfilter plates disposed in alternating fashion along the press, with saidplates being constructed so as to maintain press capacity withoutrequiring any significant increase in either the number of requiredplates or the overall size of the press, while permitting heat to beeffectively transmitted into the filter cakes formed in the filtrationchambers to effect vaporization thereof, and at the same time permittingmore effective removal of liquid or vapor from the filter cake, such asduring air blowing and vacuum-drawing cycles.

It is a further object of the invention to provide an improved filterpress, as aforesaid, which enables the heating plates to be providedwith metal heat transfer surfaces which define one side of eachfiltration chamber, with the overall construction of the remainder ofthe heat plate still employing a frame constructed principally of anon-metal material to permit forming of the heating plates in a moreeconomical and more consistent manner similar to the construction of themembrane-type filter plates.

In the improved filter press of the present invention, the press isdefined by a closable stack of filter plates defined by a firstplurality of membrane filter plates which are alternately disposed witha second plurality of heating-type filter plates. The membrane plates,as is conventional, have chamber-defining recesses on opposite sidesthereof, with each recess having a flexible membrane associatedtherewith which can be pressurized from the rearward side so as toeffect squeezing of the cake in the filtration chamber. Each heatingplate also has chamber-defining recesses on opposite sides thereof, andthe main center bottom wall of each recess has a metal heat transfersurface associated therewith, the rear side of which is in intimatecontact with a chamber or passage which receives therein ahigh-temperature heat transfer fluid.

When the press is closed, a filtration chamber is defined by opposedrecesses defined between each adjacent contacting pair of membrane andheating plates, whereby a membrane can effect squeezing of the filtercake in the chamber from one side thereof, and the heating surface onthe opposed plate can effect efficient heating of the filter cake fromthe opposite side thereof. Each of the membrane and heating plates hasporting associated therewith which communicates with preferably upperand lower extremities of the filtration chamber, with the upper andlower ports in the membrane plate preferably being substantiallydiametrically opposite the respective lower and upper ports formed inthe opposed heating plate. The diametrically opposed upper and lowerports formed in the membrane and heating plates permit air to beeffectively blown into and through the filter cake, with the air passingboth transversely across the width of the filter cake and longitudinallythrough the thickness thereof, to significantly assist in removingliquid or vapor from the filter cake. In addition, the lower portsformed in the opposed membrane and heating plates permit communicationto be established with the lower extremity of the filtration chamberadjacent both sides of the filter cake so as to permit more effectivedrainage of liquid therefrom.

In the improved filter press of the present invention, as aforesaid, theheating plates in one embodiment are defined by frames constructed of aplastics material so as to have a construction similar to the plasticframes defining the membrane filter plates, and the heat transfersurfaces are preferably defined by thin metal plates, such as ofstainless steel, which are fixed to opposite sides of the plastic frameand extend over substantially the entire bottom of the recesses formedin opposite sides thereof so as to provide a high-efficiency heattransfer surface which contacts the filter cake over substantially theentirety of one side of the filtration chamber. With this arrangement,the high-temperature heating fluid supplied to and through the interiorof the heating plate permits more effective and high-efficiency transferof heat to the metal heating plate, particularly since the plastic frameof the heating plate has a much smaller heat transfer capability andexerts minimal impact as a heat sink relative to its effect on removalof heat energy from the heating fluid.

It will be appreciated that the heating-type filter plates according tothe invention may also be used in conjunction with conventionalcloth-type chamber plates discussed above as opposed to membrane-typesqueeze plates.

Other objects and purposes of the present invention will be apparent topersons familiar with constructions of this general type upon readingthe following specification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are diagrammatic top and side views, respectively of agenerally conventional filter press incorporating therein alternatingmembrane and heating filter plates according to the present invention.

FIG. 3 is an exploded view of a portion of the filter press of FIGS. 1and 2, and showing adjacent membrane and heating filter plates.

FIG. 4 is a central longitudinally-extending cross section through fouradjacent plates shown in a closed position.

FIG. 5 is an enlarged, fragmentary cross-sectional view showing an edgeof the membrane plate.

FIG. 6 is a front elevational view of a heating plate according to thepresent invention.

FIG. 7 is a front view of the heating plate similar to FIG. 6 butshowing the plate with the heating element removed.

FIG. 8 is a front view of the heating element shown removed from theheating plate.

FIG. 9 is a fragmentary sectional view of the heating plate takengenerally along line 9-9 in FIG. 6.

FIG. 10 is a fragmentary sectional view through the heating plate takenalong line 10-10 in FIG. 6.

FIG. 11 is a front view of a heating plate corresponding to FIG. 6 butillustrating a modification thereof.

FIG. 12 is a front view of an alternate construction of the heatingplate.

FIG. 13 is a central cross-sectional view of adjacent heating plates asshown in FIG. 12.

FIG. 14 is a front elevational view of still another variation of a heatplate for use in a filter press.

FIG. 15 is a partial cross-sectional view of the heat plate shown inFIG. 14.

FIG. 16 is an elevational view of solely the frame associated with theheat plate of FIG. 14.

FIG. 17 is a cross-sectional view of the frame shown in FIG. 16.

Certain terminology will be used in the following description forconvenience in reference only, and will not be limiting. For example,the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” willrefer to directions in the drawings to which reference is made. The word“forwardly” will be used in relationship to shifting of the plates in aclosing direction, and the word “rearwardly” will refer to shifting ofthe plates in an opening direction. The words “inwardly” and “outwardly”will refer to directions toward and away from, respectively, thegeometric center of the press and designated parts thereof. Saidterminology will include the words specifically mentioned, derivativesthereof, and words of similar import.

DETAILED DESCRIPTION

As shown in FIGS. 1 and 2, there is illustrated a filter press 11 havinga pair of end supports 12 and 13 rigidly joined by a pair of generallyparallel and horizontally elongate side rails 14, which side rails aresidewardly spaced apart and cooperate with the end supports 12 and 13 todefine a generally rigid frame.

The filter press 11 has a movable follower or head arrangement 16disposed adjacent one end of the press frame and slidably supported formovement along the side rails 14. The movable head 16 is slidablydisplaceable horizontally along the side rails toward and away from afurther head 17 which is fixed to the frame adjacent the other endthereof. A drive device 18, such as a conventional double actingpressure cylinder, is mounted on the frame and cooperates with themovable head 16 for controlling movement thereof either toward or awayfrom the fixed head 17.

A plurality of filter plates, namely alternating membrane filter plates21 and heat filter plates 22, perform the filtering function of thepress. The plates 21-22 are suspendedly supported on and between theside rails 14. The plates 21-22 extend generally transversely betweenthe side rails 14 so that the plates are disposed in adjacentrelationship to form a generally horizontally extending stack of platesin the longitudinal direction of the press 11. Each plate 21-22 hassupport arms or handles 23 which project outwardly from opposite sidesof the respective plate in overlapping and slidable supportiveengagement with the upper edges of the side rails 14, thereby enablingthe plates to be slidably displaced along the side rails in thelongitudinal direction of the filter press.

As is conventional the drive device 18 is activated to move the head 16forwardly (leftwardly in FIGS. 1 and 2) so that the stack of plates21-22 is snugly and tightly held between the opposed heads 16 and 17. Inthe illustrated embodiment a suitable conduit 24 is connected to thehead 17 for communication with the interior of the stack of plates 21-22for supplying slurry or sludge therethrough into the filtration chambersdefined between the adjacent plates of the stack. A plurality ofadditional conduits 25, 26, 27, 28 also connect to the press, such as tothe head 17, for communication with passages which extend through thestack of plates, typically along the corners of the plate stack forpermitting communication with the filtration chambers for variousoperational functions during operation of the press. Such conduits 25-28typically have their own individual control valves (not shown)associated therewith to permit the desired press function to be carriedout.

To permit removal or dumping of solids (i.e. filter cake) which collectsin the filtration chambers defined between adjacent plates, the head 16is moved rightwardly in FIGS. 1 and 2 into an open positionsubstantially as illustrated in FIG. 2, and the plates 21-22 are thenindividually and sequentially moved rearwardly (rightwardly in FIG. 2)away from the stack toward the movable head 16 to permit the solidswhich collect between adjacent plates to drop downwardly for depositinto a suitable collecting bin (not shown). The sequential andindividual movement of the plates away from the stack is controlled by aconventional plate shifting mechanism.

Considering the construction of the membrane-type filter plate 21, andreferring to FIGS. 3 and 4, this plate includes a frame 29 with aringlike peripheral edge portion 31 which is generally rectangular inshape and has generally flat and substantially parallel faces located atopposite sides thereof. The frame 29 includes a center partition ordivider wall 32 which is rigidly joined to and defines the entire centerof the peripheral edge portion, with this center portion 32 in theillustrated embodiment having a center opening 33 extending transverselytherethrough. The edge frame 31 and divider wall 32 are preferablyintegral with one another, and typically comprise a molded plastic, suchas polypropylene. The center wall 32 is reduced in thickness compared tothe peripheral edge portion 31 so as to define transversely enlargedshallow recesses 36 on opposite sides thereof, which recesses 36 have arear or bottom wall 37 defined by the center partition 32. This rearwall 37 is typically provided with a non-smooth surface such as ribs ora generally rectangular array of transversely spaced projections 38.

The membrane plate 21 also includes a flexible membrane or diaphragm 39associated with and extending across each of the recesses 36. Themembrane 39 is a thin flexible sheet of liquid impermeable elastomericmaterial, for example neoprene with nylon fabric reinforcement, and hasa relatively small thickness so as to provide the membrane 39 withsignificant flexibility while at the same time providing significantheat transmission efficiency therethrough.

The diaphragm 39 is mounted on the frame 31 so as to extend across therespective shallow recess 36, and to do so the membrane has asurrounding peripheral edge part 41 which is retained in a groove 42(FIG. 5) which is formed in the face of the frame in surroundingrelationship to the respective recess 36. Suitable retaining strips orfasteners can be provided, in a conventional manner, to assist insecuring the edge of the membrane within the frame groove.

With the membrane 39 mounted on the frame 29, a squeeze chamber 43 isdefined between the diaphragm 39 and the rear wall 37 of the respectiverecess 36. To supply squeeze fluid (i.e., air or liquid) to the squeezechamber 43, the frame 31 has a transverse passage 46 formed therein andin communication with the squeeze chambers 43 defined on opposite sidesthereof, and this transverse passage 46 communicates with an inner endof a flow passage 47 which projects through the frame so as to terminateat a port 48 defined at the lower side edge of the frame. A similartransverse passage 51 is formed in the center divider wall of the frameadjacent the upper side thereof, and this passage communicates with oneend of a flow passage 52 which projects through the frame and terminatesat a port 53 defined in the upper peripheral surface of the frame. Oneof the ports, typically the lower port 48, couples to a suitable supplyconduit which supplies a squeeze fluid, such as pressurized air orliquid, into the squeeze chambers 43 disposed on opposite sides of theplate, with the squeeze fluid being discharged from the squeeze chambersthrough the upper passage 52 which at the port 53 thereof connects to asuitable discharge conduit.

The frame 29 associated with each membrane plate 21 has, adjacent thefour corners thereof, ports or passages 56, 57, 58 and 59 extendingtransversely throughout the thickness of the frame so as to terminate atthe opposite side faces thereof. These ports align with correspondingports formed in the other plates 21 and 22 when the plates are stackedtogether so as to define continuous flow passages which extendlengthwise throughout the plate stack. Appropriate seals can be providedin a conventional manner around the ports where they terminate at theside faces of the frame to create a seal between adjacent contactingplates if necessary.

At least an upper one and a lower one of the ports 56-59, and moretypically upper and lower ports disposed adjacent the same side of theframe, are also disposed for communication with the filtration chambersdefined adjacent opposite sides of the respective plate. For example,the upper port 56 communicates with a closed ended transverse passage 61which extends transversely a limited extent along the edge frame andwhich in turn communicates with a plurality of small passages or ports62 which extend transversely so as to open outwardly adjacent the frontface of the respective membrane 39 to hence communicate with therespective filtration chamber. In the illustrated embodiment two suchtransverse passages 61 are formed for communication with the port 56 andproject transversely away therefrom along the adjacent vertical andhorizontal legs of the rectangular frame so as to terminate at ports 62which open into the respective filtration chambers adjacent the uppercorner thereof.

The lower port 58 which is disposed adjacent a lower corner of the frameon the same side as the port 56 similarly communicates with one or inthe illustrated embodiment two transverse passages 63 which extend alongthe frame and, at their inner ends communicate with transverse passagesor ports 64 which are defined just forwardly of the respective membrane39 so as to provide communication with the lower corner of therespective filtration chamber.

The ports 57-59 as provided adjacent the other side of the frame 29typically function solely as flow-through passages and do not haveinternal connecting passages within the respective frame.

Both sides of the membrane plate 21 are preferably covered by a suitablethin filter cloth 66 which readily permits liquids to flow therethrough,but which restricts passage of solids therethrough. Such cloth 66 mayfor example comprise a thin sheet of woven polypropylene. The filtercloth is mounted on the frame structure so as to extend across theshallow recess and is positioned so as to extend exteriorly over theouter face of the membrane. The membrane outer surface may be providedwith a suitable texture or roughness if desired so as to permit thefilter cloth from snugly adhering thereto. The liquids (i.e., filtrate)passing through the filter cloth enter into a liquid chamber 67 which isdefined between the filter cloth and the front face of the membrane,which liquid chamber 67 at the outer edges thereof communicates with theports 62 and 64. The filter cloth 66 may extend entirely across thefaces of the plate so as to be secured exteriorly of the plate frame asdiagrammatically illustrated in FIG. 4, or may be secured to the facesof the plate frame by suitable retainer rings, such being conventionaland well known.

The construction and function of the membrane plate 21 is generallyconventional, and further detailed description thereof is believedunnecessary.

Considering now the construction of the heat plate 22, and referringspecifically to FIGS. 3-4 and 5-10, this plate includes a framestructure 69 with an outer ringlike peripheral edge frame 71 which isgenerally rectangular and has generally flat and substantially parallelfaces on opposite sides thereof. The frame structure 69 also includes adivider or center wall 72 which is rigidly joined to and extends acrossthe center of the peripheral edge frame 71, but which in the illustratedembodiment is provided with a center opening 73 disposed for alignmentwith the center opening associated with the membrane plate. In thepreferred construction the frame structure 69 is formed integrally inone piece, such as of a plastics material such as polypropylene. Thecenter divider wall 72 has a reduced thickness relative to the thicknessof the peripheral edge frame 71, resulting in the frame structuredefining shallow recesses 74 opening outwardly from opposite sidesthereof, which recesses 74 are transversely enlarged and have a bottomsurface 76 defined by the divider wall 72.

The heat plate 22 also mounts a heat transfer member 77 which isassociated with and overlies the bottom wall 76 of each side recess 74.This heat transfer member 77 is preferably formed from a material havinga high heat conductivity, and in the illustrated embodiment is formed asa thin metal plate, such as a stainless steel plate, the latterextending substantially coextensively over the entire bottom wall of therecess and having the peripheral edge portion thereof sealingly seatedon a surrounding shoulder associated with the frame structure andsecured thereto by fasteners such as screws 78.

The heating plate 22 defines therein an interior flow passagearrangement 79 for permitting a heat transfer fluid, typically a liquid,to be supplied into and circulated therethrough so as to effect heatingof the heat transfer plates 77, each of which effectively defines one ofthe side faces of the filtration chamber defined between adjacent plates21-22. The flow passage arrangement 79 for the heat transfer fluid, inthe embodiment illustrated by FIG. 7, includes a pair of passages 81 and82 which are defined on the left and right sides of the plate and ineffect each defines a generally sinusoidal passage which is formedinwardly from the bottom wall 76 of the recess 74 so as to hence beformed within the center divider wall 72. These passages 81 and 82 are,at the outer surfaces thereof, closed off by the thin heat transferplate 77 so as to enable the heat transfer fluid passing through thepassages to be brought into intimate contact with the rear surface ofthe heat transfer plate 77.

As illustrated by FIG. 7, the passages 81, 82 have the lower endsthereof in communication with a supply passage 83 which projectsoutwardly through the peripheral edge frame so as to terminate at asupply port 84, the latter being connected to a suitable conduit whichsupplies the heat transfer fluid into the interior of the heating plate.The other or upper ends of the passages 81 and 82 are connected insimilar fashion to a further flow passage 86 which terminates in adischarge port 87 disposed at the outer peripheral edge frame, thelatter connecting to a suitable discharge conduit for permitting theheating fluid to be removed from the interior of the plate. The fluidsupplied to the plate through the supply port 84 hence is effectivelydivided into two separate flows as defined by the passages 81 and 82 sothat fluid generally flows in parallel through these two passages so asto traverse vertically and horizontally throughout the interior of theplate until the flow paths again merge at the discharge passage 86.

The thin metal heat transfer plate 77 hence has the back or insidesurface thereof positioned for intimate contact with the heat transferfluid over a significant portion of the back surface area thereof sothat heat is transferred to and then through the metal plate so as tothereafter be transmitted into the filter cake disposed adjacent thefront surface of the plate. To prevent the filter cake from stickingdirectly to the heat transfer plate, however, a filter cloth 89 isgenerally provided so as to overlie each face of the heating plate,specifically so as to overlie the exterior face of the heat transferplate 77, whereby the liquid passing through the filter cloth henceaccesses a liquid chamber 91 as defined between the filter cloth and thefront surface of the heat transfer plate 77.

To further facilitate the downward flow and discharge of liquid from theliquid chamber 91, the front surface of the heat transfer plate 77 ispreferably provided with an irregular or non-smooth surface which bothprevents the filter cloth from snugly adhering thereto, and which alsodefines passages for flow of liquid thereacross. For example, in theillustrated arrangement the front surface of the heat transfer plate 77is provided with a plurality of parallel and vertically extendingshallow grooves 77A (FIG. 8) formed in the face thereof and extendingvertically thereacross so as to define channels which facilitate thedownward flow of liquid for discharge purposes. It will be appreciatedthat other structures and configurations can be provided on the frontface of the heat transfer plate so as to accomplish these sameobjectives.

The frame structure 69 of heat plate 22 also has a plurality of ports56A, 57A, 58A and 59A extending transversely therethrough betweenopposite side faces thereof in the vicinity of the four corners thereof.These ports 56A-59A are positioned so as to respectively align with theports 56-59 associated with the membrane plate 21 when the plates 21-22are disposed in alternating fashion on the press.

The ports 56A and 58A as disposed in the upper and lower corners on oneside of the frame 69 function solely as through-flow ports, and do notprovide any internal flow communication capability within the respectiveheat plate 22.

On the other hand, the upper port 57A associated with the other side ofthe heat plate 22 communicates with transverse passages 92 which, attheir inner ends, communicate with ports 93 which open sidewardlythrough both sides of the heat plate frame for communication with thecavities or recesses 74 at a location forwardly of the front face of themetal heat transfer plates 77. The lower port 59A as disposed on thesame side of the heat plate 22 similarly communicates with transversepassages 94 which at inner ends terminate with transverse ports 95 whichalso communicate with the cavities or recesses 74 at locations adjacentthe front face of the respective heat transfer plate 77. The port 57Aand its communication with the ports 93 hence provides a communicationadjacent an upper corner of the filtration cavity, whereas the port 59Aand its communication with the ports 95 hence provides communicationwith a lower corner of the filtration cavity.

The alternating arrangement of the membrane and heating plates 21 and22, when in closed alternating positions as illustrated in FIGS. 1-2 and4, thus defines a filtration chamber 96 between each adjacent pair ofplates 21-22, which filtration chamber 96 has one side thereofeffectively defined by the membrane 39 and the other side thereofdefined by the heat plate 77, with the solids being confined generallybetween the filter cloth 66 and 89. The respective upper and lower ports62 and 64 associated with the membrane plate communicate with upper andlower corners of the filtration chamber adjacent one face thereof (i.e.,adjacent the membrane plate side thereof), and also adjacent one sideedge thereof; whereas the ports 93 and 95 associated with the heatingplate 22 communicate with the opposite face of the filtration chamberadjacent upper and lower corners thereof as disposed adjacent theopposite side edge of the chamber.

The operation of the press illustrated by FIGS. 1-9 will now be brieflydescribed.

The membrane and heating plates 21 and 22 are initially alternatelypositioned on the press frame so that the ports 56, 57, 58 and 59associated with the membrane plates 21 are all aligned with one another,and are also aligned with the respective ports 56A, 57A, 58A and 59Aassociated with the alternating heating plates 22.

With the press in a closed position, the solid-liquid slurry is pumpedinto the press through the supply conduit 24 so that the slurry flowsthrough the aligned center openings 33 and 73 so as to fill thefiltration chambers 96 defined between adjacent pairs of plates 21-22.During filling of the press, the pressure of the slurry supplied to thepress effects solid-liquid separation in that a significant quantity ofliquid will typically flow through the filter cloth and thence throughthe ports 64 and 95 as respectively defined in the membrane and heatingplates and as associated with the bottom regions of the filtrationchambers, which liquid then flows into the lower ports 58-58A and59-59A, which ports define drain passages permitting the liquid to flowinto and be discharged through the conduits 26 and 28 coupled thereto.When the pressurization of the filter press results in maximum dischargeof liquid in the manner described above, there remains a relatively highconcentration of moist solids which define a filter cake between thefilter cloths of each filtration chamber 96. Thereafter subsequenttreating operations can be carried out thereon.

For example, a pressurized squeeze fluid is supplied into the squeezechambers so as to deflect the membranes 39 outwardly to effectcompression of the filter cake to assist in squeezing further liquidtherefrom.

Simultaneous with or subsequent to the squeezing of the filter cake, anair blow operation can be undertaken so as to effect removal of moisturefrom the filter cakes. During air blow, valves associated withdiagonally-opposite conduits 25 and 28 are opened so that pressurizedair can be supplied through conduit 25 into the passage defined by ports56-56A. The air in this passage is then supplied solely through theupper transverse passages 61 and ports 62 associated with the membraneplates 21 into the upper corners of the filtration chambers. The airthen flows diagonally downwardly through the filter cake thickness, andalso flows longitudinally across the filter cake, so as to access theports 95 which are located on the diametrically opposite corner of thefiltrate chamber and on the opposite face of the filter cake, whichports 95 communicate through the transverse passage 94 with the passagedefined by ports 59-59A, the latter being open to a discharge point. Theair flowing through the cake, both across the width and through thethickness thereof, is effective for removing additional moisture.

If desired, a second air blow cycle can be carried out in the oppositediagonal direction by closing the valves associated with conduits 25 and28, and opening the valves associated with conduits 26 and 27, wherebypressurized air is then supplied to the passage defined by ports 57-57Aand thence through the upper ports 93 of the heating plates, with theair flowing diagonally across and longitudinally through the filter cakeso as to access the open ports 64 on the diagonally opposite lowercorner of the membrane plates, for discharge through the passage definedby aligned ports 58-58A.

Thereafter hot heating fluid can be supplied into and through theinterior of the heat plates 22 to effect heating of the thin metal heatplates 77, which due to their intimate contact with the filter cake iseffective for heating the filter cake to a higher temperature. At thesame time a hot squeeze liquid can be supplied behind the membranes 39to not only effect expansion thereof, but to also permit at leastlimited heat transfer through the membranes to the adjacent filter caketo assist in heating the cake. Thereafter preferably the valvesassociated with all of the aligned ports 56-56A, 57-57A, 58-58A and59-59A can be opened and these ports connected to a vacuum source. Thevacuum applied to these ports is applied to the filter cakes containedwithin the filtration chambers which, in conjunction with the heating ofthe filter cakes as described above, results in lowering of thevaporization temperature of the liquid within the filter cakes so as tocause some vaporization of the liquid, which vapor is then sucked out ofthe filter cakes into the passages 56-56A through 59-59A for externaldischarge.

With the above process and in conjunction with the desirable arrangementof the heating and membrane plates, maximum drainage from the filtratechambers can be achieved since both the heating and membrane platesemploy drainage ports in communication with the filtrate chamber, and atthe same time the disposition and control of these ports in terms oftheir opening and closing greatly facilitates efficient air blow andhence moisture removal from the filter cake by permitting controlled airblow through the cake in a manner which causes the air to not only blowdiagonally across the width of the cake but also requires that the airduring its passage through the cake travel longitudinally through thecake thickness. This overall arrangement hence facilitates a moreefficient and effective removal of moisture from the cake, therebypermitting for improved drying thereof within the press.

Referring now to FIG. 11, there is illustrated a variation of a heatplate 22′ according to the present invention. The heat plate 22′ isidentical to the heat plate 22 described above except that, in thisvariation, each of the corner ports 56A, 57A, 58A and 59A hasappropriate transverse passages and communication ports associatedtherewith. That is, while the ports 57A and 59A communicate with theplate cavity through respective ports 93 and 95 as described above, theremaining ports 56A and 58A can likewise be allowed to communicate withthe cavities through additional ports 97 and 98. With this arrangement,there thus is no need to define right or left sides during initialinstallation of the heating plate on the press since the plate possessessymmetry irrespective of its directional orientation. Once installed,however, selected ones of the ports 56A-59A can be effectively isolatedfrom the plate cavities merely by installing an appropriate closureplug, such as the plugs 99 illustrated in FIG. 11, which plugs areillustrated as effecting isolation of the ports 97 and 98 from therespective ports 56A and 58A.

Referring now to FIGS. 12 and 13, there is illustrated a variation of afilter plate 110 for use in a filter press, which filter plate is ahybrid plate in that it functions both as a membrane plate and as aheating plate.

The plate 110 includes a main frame 111 typically of plastics materialsuch as polypropylene and having a rectangular outer edge frame 112integrally joined to a reduced width center wall 113, the latter in thisembodiment again having a central opening extending transverselytherethrough. This center wall 113 defines recesses 114 on oppositesides thereof which function to define a filtration cavity 116 betweentwo adjacent closed plates, as illustrated by FIG. 13. Each plate 114has a heat-transfer membrane 117 associated therewith for extension overthe respective cavity 114. The membrane 117 in this arrangement includesan outer rim part 118 which is fixed to the plate frame 111 and, in thevicinity of the outer edge of the recess 114, is provided with a flexingannulus or bellows 119 which at a radially outer edge is integrallyjoined to the rim part 118 and, at its radially inner edge is fixedlysecured, as by bonding or mechanical fasteners, to the outer peripheraledge of a thin metal heat plate 121. This metal heat plate 121, in theembodiment possessing a center opening, has its inner edge around thecenter opening secured to a further flexing annulus or bellows 122 whichhas its radially inner edge secured to the center dividing wall of theplate frame. The edge part 118 and its integrally joined bellows 119, aswell as the inner bellows 122, are preferably formed from a plasticsmaterial, such as by being molded of a thin material such aspolypropylene, and the bellows 119 and 122 are provided with a suitableconfiguration, i.e., a corrugated configuration such as a series ofinterconnected rings, so that the inner and outer bellows 119 and 122permit the heating plate 121 to move transversely away from the centerwall 113 when a squeeze liquid is supplied behind the membrane. Withthis arrangement, the squeeze liquid applied behind the membrane iseffective for displacing the membrane to effect squeezing of thefiltrate in the filtration chamber, and at the same time the heatingplate 121 (having properties similar to that described above relative tothe heat plate 77) is effective for permitting high efficiency transferof heat from the squeeze liquid to the filter cake so as to facilitateremoval of volatiles therefrom.

The modified plate 110 of FIGS. 12-13 thus carries out both the membranesqueeze function as well as the heat transfer function, and hence thepress can be equipped throughout with a plurality of identical plates.Alternatively, the plate 110 may be used in conjunction withconventional cloth-type chamber plates as discussed above in thebackground section, or with heat plates 22, 22′ illustrated in FIGS.1-11.

With the plates of FIGS. 12 and 13, the alternating plates arepreferably positioned such that the ports which communicate with thefiltration chamber are alternately positioned on opposite sides of theplate stack so as to permit air blow to be carried out in the samemanner as described above relative to FIGS. 1-10. Further, the heattransfer membrane 117 can incorporate therein drainage or dewateringgrooves similar to grooves 77A.

With the improved filter press of the present invention, it will beappreciated that utilization of separate heating plates of the typeillustrated by FIGS. 1-10 enables a significantly higher-temperatureheat-transfer fluid to be supplied to the heating plates for transfer ofheat to the filter cake. Since the material of the membranes associatedwith the membrane plates is such as to limit the temperature of thesqueeze fluid supplied to the chambers behind the membranes, theproviding of separate heat transfer plates, and the fact that they canaccommodate significantly higher temperatures, greatly improves theability to provide effective heat transfer to and heating of the filtercake so as to permit removal of vapors therefrom.

The construction of the heat plate 22 is also desirable since the thinmetal heat transfer members are confined interiorly within the plateframe when the press is closed, and the surrounding frame of plasticsmaterial functions generally as a thermal insulator so as to avoidcreating a high temperature exterior surface which can be potentiallydangerous to operating personnel. In addition, since plastic is not agood heat transfer material, it is not effective in absorbingsignificant quantities of heat from the heat transfer liquid, and hencethe heat energy from the heat transfer liquid is more readily availablefor transfer through the metal heat transfer plates to the filter cake.A higher heat transfer efficiency can thus be achieved.

While it is believed that utilization of heating plates employing a heattransfer fluid will normally be preferred in most environments employingfilter presses of this type, it will be appreciated that other means forheating the heat transfer plates can be utilized within the scope of thepresent invention. For example, the heat transfer plates 77 could beprovided with electric heaters associated therewith if desired, whichheaters can be activated only during that portion of the filtrationcycle when heating of the filter cake is desired.

When the press is of the center fill type as disclosed herein, it willbe appreciated that air blow through all four corners of the filtrationchambers may be feasible, and in such instance the air blow from thefour corners will result in the flow being directed inwardly toward thecenter of the plates, with the air blow being discharged along thecenter opening into the main center conduit.

While a center feed has been associated with the press illustrated anddescribed herein, it will be recognized that a center feed is only oneconventional technique for feeding a filter press, and that filterplates employing feeds other than a center feed can be provided. Thearrangement of the present invention is equally applicable to thosefilter presses which do not employ a center feed.

Referring now to FIGS. 14-17, there is illustrated a still furtherversion of a heat plate for use in a press according to the presentinvention. The heat plate 131 illustrated by these figures includes agenerally rectangular ringlike frame 132 constructed of a plasticsmaterial, such as polypropylene, and this frame 132 mounts therein aheat transfer assembly 133 which defines therein an interior chamber forcirculation of heat transfer fluid.

The frame 132 is similar to the previously described heat plate frame inthat the corners are again provided with ports and transverse passagesassociated therewith, and hence these will not be further described. Theframe 132, however, is not provided with a center divider wall, butrather is provided with a large opening or recess 137 which extendsentirely through the frame, which recess accommodates therein the heattransfer assembly 133. The recess 137, adjacent one side of the outeredge thereof as illustrated in FIG. 17, is bordered by a shoulder 138.

The heat transfer assembly 133 is sized and shaped so as to fit withinthe recess 137 and, as illustrated by FIG. 15, the heat transferassembly 133 includes a pair of generally parallel but thin metal heattransfer plates 141 which are sidewardly spaced apart and which aroundthe peripheral edges are rigidly joined, such as by a channel member142, so as to effectively define a closed hollow box. The interior ofthis heat transfer assembly defines a cavity or passage 145 therein foraccommodating heat transfer fluid, and in the illustrated embodiment aplurality of flow diverting elements 143 are joined to and extendtransversely between the heat plates 141 so as to define an appropriateflow path for the fluid, such as the flow path described above.

The heat transfer assembly 133 fits within the recess 137 so as to abutagainst the shoulder 138, and an appropriate heat insulating strip 146can be positioned between the frame and the heat transfer assembly. Aretaining strip 144 is then secured to the frame adjacent the other sideof the heat transfer assembly so as to rigidly retain the heat transferassembly to the frame.

As illustrated by FIG. 15, the heat transfer assembly as defined by thetransverse width across the pair of spaced heat transfer plates 141 issignificantly less than the width of the frame 132, whereby theassembled heat plate 131 hence effectively defines enlarged shallowrecesses 147 on opposite sides thereof which effectively define one sideof the filtration chamber when the heat plate is assembled into thepress.

The frame 132 is again provided with appropriate heat transfer fluidpassages extending therethrough, such as through the upper and lowerrims thereof, for communication with the heat transfer chamber 145defined by the heat transfer assembly 133.

The construction illustrated by FIGS. 14-17 results in the entire heattransfer assembly 133 being constructed of metal so as to both withstandthe high temperatures of the heat transfer fluid, and at the same timepermit efficient transfer of heat energy to the filter cakes disposed inthe filtration chambers on opposite sides of the heat plates. The metalheat transfer assembly 133, however, is still supported by andsurrounded by the plastics material defining the support frame 132, andhence the latter prevents undesired heat loss from the heat transferassembly and minimizes the temperature to which the exterior or exposedsurfaces of the filter plates 131 are subjected.

The heat transfer plate 131 can obviously be provided with otherstructural and functional features as described above, and will be usedin alternating fashion between membrane plates 21 as also describedabove.

It will be appreciated that numerous conventional variations can beincorporated into the press and filter plates according to the presentinvention. For example, while the membranes have been illustrated forsimplicity purposes as having smooth exterior surfaces, it will berecognized that these exterior surfaces are preferably provided withprojections or nibs to provide flow passages for the filtrate, suchbeing conventional in membrane construction. Also, the heat transferchamber defined behind the heat transfer plate may assume any desiredshape or configuration so as to provide for intimate and optimum contactbetween the heat transfer fluid and the heat transfer plate. Further,while the illustrated embodiment discloses the heat transfer fluid beingsupplied and discharged vertically relative to the heat plate, it willbe appreciated that the supply and discharge ports for the heat transferfluid may be oriented in whatever location or position is mostconvenient with respect to the press and the auxiliary equipment. Stillfurther, while the press as illustrated employs side bars for supportingthe filter plates, other conventional filter press arrangements can beprovided, including for example a conventional overhead support bar forthe filter plates.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

1. A filter press comprising: a frame including an elongate railstructure; first and second head assemblies supported on said railstructure adjacent respective opposite ends thereof, said headassemblies being relatively movable to permit opening and closing ofsaid press; a plate arrangement including a plurality of individualplates supported on said rail structure between said first and secondhead assemblies, said plurality of plates being disposed in a generallyhorizontally extending closed stack and clampingly held between saidfirst and second head assemblies when said press is in a closedposition; said plurality of plates comprising a plurality of firstplates each including a frame having a pair of oppositely disposedfaces, a peripheral portion, and a central portion which is recessedinwardly with respect to said peripheral portion, a pair of liquidimpermeable and flexible membranes fixed to said frame and extendingacross the respective opposite faces thereof to define respectivepressure chambers between said central portion and the respectivemembranes; and said plurality of plates comprising a plurality of secondplates each including a frame having a pair of oppositely disposedfaces, a peripheral portion, and a central portion, a pair of heattransfer members disposed within said central portion, said heattransfer members being disposed sidewardly inwardly relative to saidperipheral portion of said second plate, said central portion of saidsecond plate defining therein a chamber which communicates with a supplyof heated fluid and is disposed to bring the heated fluid within saidchamber into contact with respective inner surfaces of said heattransfer members; said first and second plates being disposed in analternating manner along said rail structure in adjacent sealing contactwith one another in said closed position of said press to definerespective filter chambers therebetween for filtering and collectingsolids from a slurry entering the respective filter chambers, each saidfilter chamber being defined on one side by a said membrane of a saidfirst plate and on the opposite side by a said heat transfer member of asaid second plate, and said pressure chambers communicating with a fluidsource to expand said membranes of said first plates towards therespective adjacent second plates.
 2. The filter press of claim 1wherein said second plates define therein a drainage passage whichcommunicates with the respective filter chamber to permit drainage ofthe liquid portion of the slurry through said second plates.
 3. Thefilter press of claim 2 wherein said first plates define therein adrainage passage which communicates with the respective filter chamberto permit drainage of the liquid portion of the slurry through saidfirst plates.
 4. The filter press of claim 1 wherein each said firstplate mounts thereon a pair of liquid permeable filter members whichoverlie the respective membranes, each said filter member and therespective adjacent membrane together defining a drainage chambertherebetween, and each said second plate mounts thereon a pair of liquidpermeable filter members which overlie the respective heat transfermembers, each said filter member of said second plates and therespective adjacent heat transfer member together defining a drainagechamber therebetween, each said first and second plate defining apassage therein in communication with the respective drainage chambersto permit drainage of the liquid portion of the slurry from oppositesides of the respective filter chambers.
 5. The filter press of claim 4wherein each said heat transfer member defines therein a plurality ofgrooves which open toward the respective adjacent filter member todefine a drainage surface across said heat transfer member.
 6. Thefilter press of claim 1 wherein said central portion of each said secondplate defines thereon a pair of oppositely facing side surfaces, andsaid heat transfer members being respectively fixed to and overlyingsaid oppositely facing side surfaces of said central portion of saidsecond plate.
 7. The filter press of claim 1 wherein said centralportion of each said second plate is hollow, and each said second platecomprises a heat transfer assembly disposed within said central portionand including said heat transfer members, said heat transfer membersbeing sidewardly spaced from one another to define therebetween saidchamber for receiving heated fluid therein to heat said heat transfermembers.
 8. The filter press of claim 1 wherein said heat transferelements are constructed of metal, and said frame of each said secondplate is constructed substantially of a non-metal material, such asplastic.
 9. The filter press of claim 1 wherein each said first platemounts thereon a pair of liquid permeable filter members which overliethe respective membranes, each said filter member and the respectiveadjacent membrane together defining a drainage chamber therebetween, andeach said second plate mounts thereon a pair of liquid permeable filtermembers which overlie the respective heat transfer members, each saidfilter member of said second plates and the respective adjacent heattransfer member together defining a drainage chamber therebetween, eachsaid first and second plate defining porting therein including upper andlower ports, said upper and lower ports of said first plates beingdisposed diametrically opposite the respective lower and upper ports ofthe adjacent said second plate, said porting of said first and secondplates communicating with the respective drainage chambers to permitdrainage of the liquid portion of the slurry from the respective filterchambers.
 10. The filter press of claim 9 wherein said porting of saidfirst and second plates additionally permits air blow through a filtercake disposed in a said filter chamber such that the air passes bothtransversely across the width of the filter cake and longitudinallythrough the filter cake.
 11. A filter press for separating liquid from aslurry, said press comprising: a horizontally extending stack of platesdisposed in side-by-side relation and supported on an elongate supportframe which permits opening and closing of said stack, said plates beingclampingly held together in sealed relationship with one another by saidsupport frame to define a closed position of said press; said stack ofplates comprising first plates each including a rigid frame having apair of oppositely disposed faces and being recessed inwardly onopposite sides thereof, said frame mounting thereon a pair of liquidpermeable filter members which extend across the respective recesses ofsaid frame to define respective drainage chambers, said stack furthercomprising second plates disposed in an alternating fashion with saidfirst plates, each said second plate including a rigid frame having apair of oppositely disposed faces and including thereon a pair of heattransmitting surfaces on respective opposite sides thereof, said heattransmitting surfaces being recessed inwardly relative to a peripheralportion of the respective second plate, the adjacent first and secondplates together defining a filter chamber therebetween, and each saidfirst and second plate defining ports therein in communication with therespective drainage and filter chambers to permit drainage of liquidfrom the slurry through both said first and second plates.
 12. The pressof claim 11 wherein said frame of each said second plate includes acentral wall having opposite sides on which the respective heattransmitting surfaces are defined, said central wall defining thereinheating passages disposed to conduct heated fluid along the respectiveheat transmitting surfaces to heat same and a filter cake formed in therespective filter chamber.
 13. The press of claim 11 wherein said frameof each said first plate includes a central portion surrounded by aperipheral portion, said central portion being recessed inwardlyrelative to said peripheral portion, each said first plate mountingthereon a pair of liquid impermeable membranes each disposed betweensaid central portion and a respective said filter member, each saidmembrane and said central portion together defining a pressure chambertherebetween for receiving pressurized fluid to expand said membranetowards the respective second plate.
 14. The press of claim 11 whereineach said second plate mounts thereon a pair of liquid permeable filtermembers which overlie the respective heat transmitting surfaces, eachsaid second plate defining a drainage chamber between each said filtermember and the adjacent heat transmitting surface, and each said heattransmitting surface defining therein drainage grooves which opentowards the respective filter member.
 15. A plate for a filter press forseparating liquid from a slurry, said plate comprising: a rigid frameincluding a peripheral portion disposed in surrounding relation with acentral portion, said central portion having a width which is less thansaid peripheral portion such that inwardly projecting recesses arerespectively defined on opposite sides of said frame; and a pair of heattransfer elements disposed on opposite sides of said frame and withinthe respective recesses, each said heat transfer element comprising anouter peripheral portion fixed to said frame and defining a flexiblebellows, and a metal heat plate fixed to an inner edge of said bellowsand extending across the respective recess of said frame, each side ofsaid central portion and the adjacent said heat transfer elementtogether defining a chamber which communicates with a supply of heatedfluid to provide intimate contact between the heated fluid and an innersurface of the respective heat plate.
 16. The filter plate of claim 15wherein said frame defines therein a flow passage arrangement whichcommunicates with respective filtrate chambers defined at respectiveoutwardly facing side surfaces of said heat transfer elements, said flowpassage arrangement additionally communicating with a liquid dischargeconduit to permit drainage of liquid from the slurry through said plate.17. A plate for a filter press for separating liquid from a slurry, saidplate comprising: a frame including an outer peripheral portion disposedin surrounding relation with a central portion, said frame beingconstructed of a material having a low heat conductivity, said centralportion having oppositely facing sides which are recessed sidewardlyinwardly relative to said peripheral portion; and a pair of heat platesfixed to the respective sides of said central portion so as to overliesame, said heat plates being disposed sidewardly inwardly relative tosaid peripheral portion so as to define part of a filtration chamberwhen disposed adjacent another filter press plate, said sides of saidcentral portion of said frame defining therein flow passages whichreceive heated fluid and transport the heated fluid into intimatecontact with the respective said heat plates to heat same.
 18. The plateof claim 17 wherein said plate defines therein a port arrangement whichcommunicates with the respective filtration chambers to permit drainageof liquid portion of the slurry through said plate and to permit airblow of cakes formed in the respective filtration chambers to dry same.19. The plate of claim 18 wherein each said heat plate defines thereonan irregular surface to prevent sticking of the filter cake thereto andto provide a drainage area for liquid portion of the slurry.
 20. Theplate of claim 19 wherein said irregular surface comprises a pluralityof grooves which open sidewardly towards the respective filtrationchamber.